Sidewall Thickness Research Articles

Multi-pass deep-drawing process and mould design for thin-walled hollow cylindrical parts

Thin-walled hollow cylindrical parts are widely employed in various industries, including automobiles, ships, and aviation, due to their increased demand and the escalating quality requirements for their formation. The production of these parts primarily relies on a multi-stage deep drawing process. However, during the deep drawing process, the gradual reduction in the side wall thickness creates a susceptible area at the bottom rounded transition, where local over-thinning may occur, thereby increasing the risk of cracking. Furthermore, the deep-drawing process becomes more intricate for thin-walled hollow cylindrical parts with a large height-to-diameter ratio, amplifying the likelihood of defects during actual production. This paper combines CAE simulation and empirical design to comprehensively investigate and analyze the multi-stage deep drawing process and mold design for thin-walled hollow cylindrical parts. The aim is to optimize the deep-drawing process and mold parameters, enhance the products qualification rate, and provide valuable guidance for the practical production of relevant enterprises.

Mask 3D parameter optimization for improving imaging contrast of plasmonic lithography

Based on plasmonic lithography (PL) technology, and aiming at the special nano-optical effect of metal/dielectric multilayer composites and mask three-dimensional (M3D) effect, a method for optimizing mask parameters is proposed. As a common analytic formula, the optical transfer function method has been introduced to analyze the imaging process. In order to include the M3D effect, FDTD is used to quantitatively calculate the PL imaging results, and the aerial image (AI) intensity and the light intensity contrast of AI in the photoresist layer can be obtained. The simulation results suggest that the imaging resolution and light intensity contrast can be improved by optimizing the M3D parameters such as the sidewall angle, thickness, and material of the mask absorber. For the line space test pattern with critical dimension = 150 nm and pitch = 300 nm, the results indicate that the optimal sidewall angle is 40°, resulting in an increase in the light intensity contrast of 344%. The light intensity contrast with a mask thickness of 70 nm is improved by 11% when compared to a mask thickness of 60 nm. The use of Ta and opaque MoSi on glass as the mask absorber material improves the light intensity contrast to varying degrees compared to the Cr mask.

Optimization design of thermal protective characteristics of special- shaped honeycomb structure

This study addresses the thermal protection challenges during the flight of aircraft by proposing an actively cooled specially shaped honeycomb structure that integrates heat insulation and load-bearing capabilities. We conduct numerical simulations to analyze the parameters influencing the structure's flow and heat transfer characteristics. In addition, we perform an optimization design using an orthogonal experimental approach. The results indicate that under constant flow rates, the average inlet and outlet pressure drop (ΔP) decreases with increasing channel width (W) and increases with growing channel sidewall thickness (δ) and the length of the middle section of the channel (L2). The convective heat transfer coefficient (have) decreases with increasing (W) and increases with augmenting individual (δ) and (L2). The maximum equivalent stress increases with increasing (W) and decreases with growing (δ). When (δ) is set to 0.065 mm, W = 1.2 mm and L2 = 1.2 mm. Consequently, the comprehensive heat transfer factor (j) is maximized, and the flow heat transfer characteristics are optimal.

Structural Analysis of Thermal Diffusion and Non-Uniform Temperature Distribution along the Sidewall Thickness of STS316L during Gas Tungsten Arc Butt Welding

This study investigated how welding affects the thermal deformation of square cells produced for casks, which are dry storage containers for spent nuclear fuel. We aimed to minimize structural deformation by utilizing STS316L as the material for the square cells. We explored a method of subdividing the square cells and joining them through butt welding. Keeping the upper plate thickness constant, GTA butt welding was conducted while varying the column’s wall thickness, followed by measurement with a laser vision sensor. The heat conduction and thermal strain were then calculated using a finite element analysis (FEM). Both experimental and analytical results confirmed that there was significant thermal deformation in the cases of thick-walled columns due to variations in heat conduction distribution, with the resulting deformation patterns depending on thickness.

The Thermal Field Design of a 150 mm Sic Crystal Growth System by Numerical Simulation

AbstractNumerical simulation analysis, enabled by the physical vapor transport (PVT) technique, has been widely adopted to study the growth process of silicon carbide (SiC). In this study, a 2D axisymmetric model employed the finite volume method (FVM) is adopted to simulate the thermal fields and mass transfer of SiC powders with different particle sizes, thicknesses of the top thermal insulation, side wall thicknesses of the lid, and distances between the lid center and the top thermal insulation in a SiC crystal growth system. The simulation results revealed that the reduction in particle size increased the radial and axial temperature gradients in the powder region. Meanwhile, when the thickness of the top thermal insulation decreased, the axial temperature gradient inside the crucible increased significantly. Furthermore, the change in the side wall thickness of the lid significantly affected the thermal field distribution on the crystal surface and consequently affected the crystal growth shape. Finally, the variation in the distance between the lid center and the top thermal insulation has a significant influence on the axial and radial temperature gradients. Overall, these results indicate that the quality of SiC crystal growth may be improved by adjusting particle size, thermal insulation and crucible design.

Multi-scale damage modeling and out-of-plane shear behavior of carbon/carbon honeycomb structure

In response to the demand for the ultra-high stability and light-weight optical structure in high-resolution spacecraft, the present study proposes a novel carbon/carbon (C/C) honeycomb structure which integrates the superiorities of C/C composite and honeycomb structure. The C/C honeycomb was fabricated by chemical vapor infiltration (CVI) processing with continuous carbon fiber preform, and then the L- and W-direction shear experiments were conducted. A multi-scale damage model is established to describe the mechanical and damage behavior of the C/C honeycomb, which includes the damage model and constitutive model in both meso-scale and macro-scale. The effects of yarn orientation, side length, wall thickness and height of C/C honeycomb on L- and W-direction shear characteristics as well as damage modes of the novel C/C honeycomb are comprehensively researched. The results show that the C/C honeycomb has excellent shear properties when the yarn orientation is ±45° as well as the side length and wall thickness are about l=6mm and t=0.3mm, respectively. With the yarn orientation shifts from 0°/90° to ±45°, the damage region transforms from top and bottom surfaces of the C/C honeycomb structure to honeycomb walls. As the side length increases and the wall thickness decreases, the damage region is distributed obliquely along the honeycomb wall. This research contributes to the design and optimization of optical-mechanical structures in high-resolution spacecraft.

Structural investigation of ultra-low resistance deeply recessed sidewall ohmic contacts for AlGaN/GaN HEMTs based on Ti/Al/Ti-metallization

This study presents a novel approach to forming low-resistance ohmic contacts for AlGaN/GaN HEMTs. The optimized contacts exhibit an outstanding contact resistance of approximately 0.15 Ω·mm. This is achieved by firstly recessing the barrier of the heterostructure to a depth beyond the channel. In this way, the channel region is exposed on the sidewall of the recess. The coverage of the Ti/Al/Ti ohmic metalization on the sidewall is ensured through tilting of the sample during evaporation. The annealing process is performed at a low temperature of 550 °C. The approach does not require precise control of the recess etching. Furthermore, the method is directly applicable to most barrier designs in terms of thickness and Al-concentration. The impact of recessed sidewall angle, thickness and ratio of Ti and Al layers, and the annealing procedure are investigated. Structural and chemical analyses of the interface between the ohmic contacts and epi-structure indicate the formation of ohmic contacts by the extraction of nitrogen from the epi-structure. The approach is demonstrated on HEMT-structures with two different barrier designs in terms of Al-concentration and barrier thickness. The study demonstrate large process window in regard to recess depth and duration of the annealing as well as high uniformity of the contact resistance across the samples, rendering the approach highly suitable for industrial production processes.

Conjugate local thermal nonequilibrium and non‐Darcy flow inside porous enclosure: Analysis of localized heating and cooling arrangements

AbstractThis study covers a simulation on conjugate free convective in a porous enclosure containing a side wall thickness and partially heated and cooled from sides under the considerations of local thermal nonequilibrium (LTNE) and non‐Darcy flow. Interest has been focused on how the side wall thickness and the locations of cooled and heated parts affect the effectiveness of the Nusselt number (Nu). Three different cases of localized heating and cooling locations have been implemented for the following ranges: scaled heat transfer coefficient (), wall to fluid thermal conductivity ratio (), modified Rayleigh number (), wall width (), inertial parameter (), and thermal conductivity ratio (). Outcomes show that and the locations of cooled and heated parts have remarkable impacts on all the Nusselt numbers. The intensity of LTNE region considerably relies on , and . The total average NuT is highly dependent on , , , , and as compared to H. The increase in leads to change of the convective mechanism to conductive mode. The rise in guides to increase Nu, where can control the flow strength. The actions of on Nuf is more evident than Nus. For low H and Kr, the size of LTNE zone is considerably affected by H as compared to Kr although Kr has a high influence on Nu. For high Kr and H, the LTNE zone has closely vanished. Findings display that the Case 2 provided the highest Nu for all tested parameters except the case of . Finally, it is evident that for the problems that employed solid conduction wall with localized heating and cooling sections, Case 2 is recommended for future use in the applications that implement a porous medium and depend on free convection.

Investigation on the wall thickness variation of an eccentric tube in the rotary draw bending process

PurposeWhen bending a large diameter thin-walled tube, the thickn ess of outer side wall will reduce greatly, which leads to a decrease of structural strength of the tube. To solve this problem, this paper investigated the deformation principles of an eccentric tube in the rotary draw bending process, trying to find a way to reduce the wall thickness difference between inner and outer diameters.Design/methodology/approachAn finite element model is established for analyzing the deformation of an eccentric tube in rotary draw bending process. The wall thickness distribution of the formed pipe was analyzed along the axis and diameter, respectively.FindingsIt is found that there exists an optimal eccentricity between the inner and outer circle center of the tube cross-section. If the eccentricity of the tube is chosen properly, it is possible to get a bent tube with equal thickness of inner and outer side walls. In addition, it is also found the optimal eccentricity on the cross-section can be influenced by bending radius, wall thickness, diameter and bending angle. The optimal eccentricity increases greatly with the decreasing of bending radius, the increase of outer diameter and the increase of wall thickness. The influence of bending angle on the optimal eccentricity can be divided into two situations. When the bending angle is small, the optimal eccentricity increases with the increase of bending angle. When the bending angle exceeds a certain value, the pipe enters a stable forming state. The optimal eccentricity of the stable forming region does not change with the bending angle.Originality/valueSuch a research is beneficial for reducing the thickness difference between inner and outer side walls in the rotary draw bending process.

Prediction of internal fixation failure of femoral trochanteric fracture by external wall morphology

To investigate the relationship between the shape of the lateral wall and the early failure of internal fixation in the fracture of the femoral trochanteric region(FFT). Total 295 patients with femoral trochanteric fracture underwent internal fixation from January 2015 to January 2020 were selected. The patients were divided into two groups according to whether there was early internal fixation failure after surgery, 19 patients in the failure group and 276 patients in the normal group. Gender, affected side, age, AO classification, body mass index(BMI), preoperative hemoglobin, X-ray measurement of lower lateral wall thickness, preoperative internal diseases, intraoperative blood loss, postoperative tip apex distance(TAD), postoperative neck shaft angle, operation time and other data were compared between two groups. The shape of the lateral wall was compared between two groups, and the correlation between the shape of the lateral wall and the early internal fixation failure of femoral trochanteric fracture was analyzed. All patients were followed up for more than 1 year. There was no significant difference between two groups in terms of intraoperative blood loss, operation time, postoperative TAD, and postoperative neck shaft angle(P>0.05). At the latest follow-up, the visual anaglue scale (VAS) of the failure group was higher than that of the normal group(P<0.01), and the Harris score of the failure group was lower than that of normal group(P<0.05). The receiver operator characteristic (ROC) curve between shape of lateral wall and failure of early internal fixation of femoral trochanteric fracture was drawn. The critical value of the midpoint lateral wall thickness was 16.5 mm, and the area under the ROC curve was 0.845;The critical value of average sidewall thickness was 16.5 mm, and the area under ROC curve was 0.838;The critical value of the axial area of the sidewall was 7.5 mm, and the area under the ROC curve was 0.826. The shape of the lateral femoral wall measured by CT could be used as a predictive factor for the early failure of internal fixation of femoral trochanteric fractures. For patients at risk, more reasonable surgical plans and postoperative preventive measures should be developed.

Dynamic Response of Outer Windshield Structure in Different Schemes under Aerodynamic Load

With the increase in high-speed train (HST) operation speed, the light-weight design of the train body and component structure is pursued to reduce energy consumption during operation, but this seriously deteriorates the aerodynamic performance of the light-weight structure outside the train body under the effect of strong unsteady airflow, and the more obvious case is the frequently occurring problem of vibration, large deformation, and damage to the rubber exterior windshield at the connection position of HST carriages. We investigate the fluid–structure coupling mechanism of the interaction between the rubber external windshield and aerodynamic force, and compare the dynamic characteristics of windshield structure under different design parameters. A numerical simulation of three rubber outer windshield structure parameters (sidewall distance of U-shaped capsule, sidewall thickness, sidewall inclination angle) is carried out using FSI simulation of the two-way coupling method. The aerodynamic load, airflow dynamics around the windshield, and the nonlinear vibration and deformation form of the windshield is analyzed in detail. The results show that the aerodynamic response of the HST rubber external windshield analyzed by the FSI method is in good agreement with the full-scale test results. Additionally, the stiffness of the windshield can be improved by increasing the thickness of the windshield sidewall. When the distance between the sidewall of the windshield is increased, an insufficient thickness at the top of the arc causes a large local deformation at the top of the arc of the windshield. The method established and relevant research results can provide good support for the aerodynamic stability evaluation of HST windshields.

Temperature Field and Stability Analysis of the Frozen Wall Based on the Actual Position of Freezing Holes

Taking the Qingdong Mine as the research object, combined with field measurement data, numerical simulation and theoretical analysis are used to examine the temperature field and stability of the frozen wall in the mine, respectively. The results show that during the active freezing period, under the same freezing time, the average temperature of the effective frozen wall of the fine sand layer is 0.2–1.0 and 0.5–2.5 °C lower than that of the sandy clay layer and clay layer, respectively. The effective frozen wall thickness of the fine sand layer is 0.04–0.17 and 0.17–0.33 m larger than that of the sandy clay layer and clay layer, respectively. The soil cooling between the two circles of freezing holes is the fastest. Due to the deflection of the freezing holes, the interface temperature field is asymmetrical. For deep clay with a depth of 200–250 m, it is most economical and reasonable for the brine temperature in the active freezing period to be −25 and −30 °C. At the designed brine temperature for cooling, during the excavation of the control layer of the topsoil layer (−216 m sandy clay), the side-wall temperature, average temperature, and thickness of the frozen wall meet the design requirements. The ultimate bearing capacity of the frozen wall is 3.20 MPa. When the well is empty for 30 h after excavation, the maximum radial displacement is 26.85 mm, so the frozen wall strength and stability are in a safe state. Overall, the findings of this study can serve as a useful reference for similar freezing projects.

Construction of soft polyurethane cushioning composites based on integral fabric air layer: Reaching new levels in compression and cushioning behaviors

AbstractIn order to prepare a cushioning composite with good resilience and compressibility, the 3D fabric was perforated into a hexagonal honeycomb, high elasticity porous polyurethane foam was used as substrate, and the air layer structure was encapsulated with the packaging film. By changing the hexagonal side length and wall thickness of the honeycomb structure, the integral fabric air layer polyurethane buffer composite was prepared. The properties of the structure were studied, and its compressive capacity under different compressive strains was analyzed. The results show that the mechanical properties of polyurethane foam were improved after adding the integral fabric air layer structure. When the composite HPU‐R1L2 (polyurethane cushioning composites with 1 cm side length and 2 cm wall thickness of hexagonal honeycomb) was compressed to 75%, its compressive capacity was 8.24 times that of PU (Polyurethane foam with 2.5% bentonite). The prepared composite HPU‐R1L1 (Polyurethane cushioning composites with 1 cm side length and 1 cm wall thickness of hexagonal honeycomb) absorbed 96.7% of the energy in the dynamic impact test, indicating that the composite cushioning performance was stronger than that of polyurethane foam. The HPU composites based on the synergistic reinforcement strategy of polyurethane foam and monolithic fabric air‐layer structures are an excellent candidate in the field of commodity packaging and personal protection.

Premixed syngas/air combustion in closed ducts with varied aspect ratios and initial pressures

Syngas is a promising renewable energy carrier, and its combustion can result in a significant reduction of pollutant emissions. However, syngas has various production sources, its compositions are diverse accordingly. That brings some challenges in its practical application. Therefore, in order to deeply investigate the premixed stoichiometric syngas/air combustion in confined spaces, experiments were conducted in a closed duct with varied aspect ratios (12, 26 and 40) and initial pressures from 0.5 atm to 1.5 atm. Flame shape evolutions in varied cases were captured through high-speed photography, and four flame speed oscillation regimes were distinguished qualitatively. The pressure buildup was recorded by sensors and scrutinized by dimensionless method. The results denoted the propagation dynamics became more violent with higher initial pressure or aspect ratio. Further, the combustion instability was examined, and it indicated the acoustic effect and the Rayleigh-Taylor/Richtmyer-Meshkov instability would be stronger in cases with large aspect ratio, resulting in the deformation of elongated tulip flame. Besides, the Bychkov's theory considering gas compression effect was validated by the experimental data. The discrepancy between them was interpreted with a comprehensive view of enlarged laminar burning speed, non-adiabatic sidewall and finite flame front thickness.

Experimental and simulation research on hollow AZ31 magnesium alloy three-channel joint by hot extrusion forming with sand mandrel

Magnesium alloy is one of the lightest metal structural materials. The weight is further reduced through the hollow structure. However, the hollow structure is easily damaged during processing. In order to maintain the hollow structure and to transfer the stresses during the high temperature deformation, the sand mandrel is proposed. In this paper, the hollow AZ31 magnesium alloy three-channel joint is studied by hot extrusion forming. Sand as one of solid granule medium is used to fill the hollow magnesium alloy. The extrusion temperatures are 230 °C and 300 °C, respectively. The process parameters (die angle, temperature, bottom thickness, sidewall thickness, edge-to-middle ratio in bottom, bottom shape) of the hollow magnesium alloy are analyzed based on the results of experiments and the finite element method. The results are shown that the formability of the hollow magnesium alloy will be much better when the ratio of sidewall thickness to the bottom thickness is 1:1.5. Also when edge-to-middle ratio in bottom is about 1:1.5, a better forming product can be received. The best bottom shape in these experiments will be convex based on the forming results. The grain will be refined obviously after the extrusion. Also the microstructures will be shown as streamlines. And these lines will be well agreement with the mold in the corner.

Comparison of spinning trajectory designing methods for products with noncircular cross-section

Abstract This article provides information about comparative research on designing of spinning trajectories for products with a non-circular cross-section. Generation of two outlines for the two mandrels was carried out using three methods: (1) a spreadsheet, (2) a 2D CAD program, and (3) a 3D CAD program. Technological tests were carried out using mandrels with the following geometries: ellipse and square. The material used in the research was aluminum Al 1050A. Due to the high degree of complexity in the design of the trajectory, Method 1 was used only for spinning of the ellipse. Methods 2 and 3 were used for spinning the square. Only Method 3 was suitable for programming of upsetting moves of tool. Test of Vickers's microhardness was conducted on sample 3. The influence of the spinning trajectory on the drawpiece was evaluated by measuring the percentage reduction of side wall thickness.

Effect of modeling sidewalls on tire vibration and noise

Low-noise tire design demands the potent model, which regards accessible parameters in the design process before manufacturing a tire. Unlike most previous analytical models that integrated tire treadband with sidewalls with an assumption of identical properties, this research segregates them. The separation clarifies the effects of each tire part on vibration and noise individually, which has not been presented in previous publications and is noteworthy in design. The model is developed considering three connected plates, describing treadband and sidewalls, on an elastic foundation derived from vibro-acoustic coupling inside the tire. Natural frequencies are determined by the Galerkin method using modes shapes satisfying all boundary conditions. The vibration response of a tire rolling on the road is then formulated utilizing Green’s function and convolution integral. Eventually, vibrational tire noise is calculated by the boundary element method. Comparing the proposed model with the repeatedly used integrated plate model has indicated the dissimilarity of treadband and sidewall responses with a difference of 1.4 dB(A) in total noise level. Moreover, implemented parametric study based on a small central composite design has revealed their parameters’ distinct influences on generated noise. For instance, increment in treadband thickness reduces sound level, while decreasing sidewall thickness effectively leads to noise reduction. So, the proposed model is worth employing instead of the previous overused integrated model to predict and reduce tire noise.

Experimental and analytical models of flexural behavior of U-shaped reactive powder concrete permanent beam formworks

The primary purpose of this study was to analyze the application of reactive powder concrete (RPC) in U-shaped permanent beam formworks. Experiments were conducted to investigate the mechanical (compression and tensile) properties of RPC and the flexural capacity of permanent formworks. Six U-shaped permanent beam formworks were tested under four-point flexural loading until failure. Additional parameters such as side wall thickness, bottom board thickness, and the reinforcement ratio were analyzed to investigate the flexural behavior of the formworks before pouring. The moment capacity, load-deformation curve, and failure process and mode of the specimens were examined. All the specimens failed the flexural test and exhibited a bending failure mode similar to that of concrete beams. The test results revealed that increasing the thickness of the bottom board of the U-shaped RPC permanent formwork was effective in delaying the cracking moment of the U-shaped formwork. We created analytical models to calculate the cracking moment of U-shaped RPC permanent beam formworks. A comparison of the analytical and experimental results revealed that our simplified analytical model predicts the experimental results better than existing models do.

MECHANICAL PROPERTIES ANALYSIS OF A NEW ENERGY ABSORBING STRUCTURE WITH NEGATIVE STIFFNESS

As a kind of mechanical metamaterial with wide application prospect, negative stiffness structures show significant advantages in energy absorption, vibration attentuation, and noise reduction . However, their engineering applications are severely limited attributed to the low specific energy absorption efficiency and non-autonomous spring-back of negative stiffness structures with the speciality of multi-stability. In order to solve this problem, by means of cell configuration design, a new kind of three-dimensional negative stiffness structure with the characteristic of autonomous spring-back is proposed in this paper. For this negative stiffness cells in series, the self rebound of curved beams during the loading and unloading process is used to realize the cyclic loading and multiple reuse of the structure.The multi-stability is restrained by adding a groove of certain depth. The buckling mode is selected via the adjustment of side wall thickness. The difference between critical loads of negative stiffness is thus enlarged, accordingly, the energy absorption efficiency is significantly improved. Then in order to achieve high energy absorption under complex load environments, the gradient design of structure size is carried out, and a gradient negative stiffness structure is proposed. The energy absorption efficiency of gradient negative stiffness structure and uniform negative stiffness structure under different load cinditons is compared by finite element simulations. Analytical and numerical results reveal that for the newly developed negative stiffness structure, not only the feature of autonomous spring-back is achieved, but also the energy absorption ability is improved. Moreover, different critical load maximums for negative stiffness are obtained for the gradient structure due to different microstructure sizes, which makes it to exhibit better energy absorption efficiency on the basis of realizing autonomous spring-back under various impact load environments. The new energy-absorption structure proposed in this paper provides technical support for engineering applications such as vibration attenuation and structure reorganization.

Structural Parameter Analysis of Self-Tightening Metal U-Shaped Seal Ring

The effects of different structural parameters on the sealing performance of self-tightening metal U-shaped seal rings were studied. A two-dimensional axisymmetric model of a self-tightening U-shaped seal ring was established using finite element software. The influence of structural parameters such as side wall thickness, bottom wall thickness and boss radius on the sealing performance of the seal ring was analyzed by the control variable method. The results show that as the thickness of the side wall increases, the stress shows a downward parabolic trend, which is the smallest at 0.55 to 0.65 mm; as the bottom wall thickness increases, the stress first increases steadily, and then decreases slowly after 0.8 to 0.9 mm; When the inclination angle is from 0 to 9 °, the sealing ring can obtain better sealing performance. The results have guiding significance for the design, optimization and application of subsequent seal ring structures.